# What coordinate systems are there?
1.WGS-84 original coordinate system, generally using the longitude and latitude recorded by international GPS recorders, the original longitude and latitude obtained through GPS positioning, the longitude and latitude positioned by Google and Amap (overseas) are all based on the WGS-84 coordinate system; however, in China, it is not allowed to directly use the WGS84 coordinate system for labeling, and it must be encrypted before it can be used;2. The GCJ-02 coordinate system, also known as the "Mars coordinate system", is an original coordinate system created by my country's National Bureau of Surveying and Surveying. It is encrypted by WGS-84. In China, at least the GCJ-02 coordinate system must be used, or a coordinate system that is encrypted after GCJ-02 encryption, such as the Baidu coordinate system. Amap and Google both use the GCJ-02 coordinate system in China. It can be said that GCJ-02 is the most widely used coordinate system in China;
3.Baidu coordinate system: bd-09, Baidu coordinate system is a coordinate system formed by re-encrypting and shifting based on the GCJ-02 coordinate system. It is only applicable to Baidu maps. (Currently, Baidu API provides an API for converting from other coordinate systems to Baidu coordinate systems, but there is no API for converting from Baidu coordinate systems to other coordinate systems);#
# Query latitude and longitude online
[http://www.gpsspg.com/maps.htm](http://www.gpsspg.com/maps.htm)
[https://lbs.qq.com/getPoint/](https://lbs.qq.com/getPoint/)
[https://lbs.amap.com/console/show/picker](https://lbs.amap.com/console/show/picker)
[http://api.map.baidu.com/lbsapi/getpoint/index.html](http://api.map.baidu.com/lbsapi/getpoint/index.html)
Through the above URL, you can query the GPS longitude and latitude coordinates corresponding to the specified map coordinates.
# Coordinate system conversion
[https://www.opengps.cn/Map/Tools/GPSConvert.aspx](https://www.opengps.cn/Map/Tools/GPSConvert.aspx)
Through the above URL, the conversion between the WGS84 coordinate system and the GCJ02 coordinate system can be achieved
# Extra
You can use the mobile phone positioning to get the WGS84 positioning, and then through the above coordinate system conversion, you can get the GCJ02 coordinate system that can be used in the software